Fibronectin is a large glycoprotein, about 450 thousand daltons, which is composed of several apparently independent functional domains. Fibronectin was earlier discovered as a major extracellular matrix protein, and it was demonstrated that it would interact in vitro with other structural molecules, such as collagen, glycosaminoglycans, proteoglycans, fibrinogen, fibrin, and actin, as well as with cell surfaces. It was discovered that fibronectin promotes the attachment of suspended cells to collagen and also that it promotes the attachment of suspended cells directly to tissue culture substrate, independent of its binding to collagen. Accordingly, investigation continued with respect to the region of the fibronectin molecule that interacts with cell surfaces.
Earlier, a polypeptide fragment of fibronectin which embodies the cell attachment activity of fibronectin was isolated, purified and characterized as a 11.5 kDal polypeptide of 108 amino acid residues, and having the formula: H-Ile-Gly-Gln-Gln-Ser-Thr-Val-Ser-Asp-Val-Pro-Arg-Asp-Leu-Glu-Val-Val-Ala- Ala-Thr-Pro-Thr-Ser-Leu-Leu-Ile-Ser-Trp-Asp-Ala-Pro-Ala-Val-Thr-Val-Arg-Tyr -Tyr-Arg-Ile-Thr-Tyr-Gly-Glu-Thr-Gly-Gly-Asn-Ser-Pro-Val-Gln-Glu-Phe-Thr-Va l-Pro-Gly-Ser-Lys-Ser-Thr-Ala-T r-Ile-Ser-Gly-Leu-Lys-Pro-Gly-Val-Asp-Tyr-Thr-Ile-Thr-Val-Tyr-Ala-Val-Thr- Gly-Arg-Gly-Asp-Ser-Pro-Ala-Ser-Ser-Lys-Pro-Ile-Ser-Ile-Asn-Tyr-Arg-Thr-Glu -Ile-Asp-Lys-Pro-Ser-Gln-Met-OH. Also, a fragment of the foregoing molecule having the same cell attachment activity was synthesized and is comprised of 30 amino acid residues having the formula: H-Tyr-Ala-Val-Thr-Gly-Arg-Gly-Asp-Ser-Pro-Ala-Ser-Ser-Lys-Pro-Ile-Ser-Ile- Asn-Tyr-Arg-Thr-Glu-Ile-Asp-Lys-Pro-Ser-Gln-Met-OH. (These fragments have been described in the aforesaid patent applications.) These polypeptides, or a fragment thereof which has cell attachment activity, can be used to prepare substrates to which cells will attach. Such substrates are useful in cell culture dishes and are also useful for employment in medical prosthetic devices for implanation in the human body where enhanced cell attachment to the surface is desirable.